There are many factors with service scheduling and it all comes back to the whole service department that could delay your appointment.
Customer preference, Wrong or not enough parts ordered, Workers not showing up for work, Unexpected problems, Untrained Technicians causing customers to return for the same service right away, all this has a chain reaction for people waiting for service. My opinion is that, if you have to wait much longer than your appointed service date
go somewhere else if possible.:M